Should I use an iridium plug?

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Hey, I have a 2007 yz250(285 map power) I was curious to if I could/should use NGK's new Iridium plug. The plus i have pulled up for my 07 yz250 is a BR8EIX(iridium plug by NGK) i currently run a BR8EG by NGK.

Thanks

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I really don't feel the YZ250 is picky on plugs like some bikes. I think you'll find in the Yamaha 2 stroke forum that a large number of us just use the plain ol BR8ES plug with great success. I littrally have gone a 50 hour top end on one plug. The only time I might change them in between there is if I'm doing major jetting changes (like for winter) and want to get a good read from a new plug. I never noticed a difference in performance between the irridium or std plug in my bike.

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The reason for the use of exotic/precious metals like iridium in spark plug electrodes is to improve spark strength at the margins. They won't improve power unless they can prevent a misfire.

When the coil is fired, there is an abrupt rise of voltage in the center electrode. To make an analogy to hydraulic circuits, voltage is pressure, and is referred to as electromotive force. The pressure builds until it is great enough to burst through the resistance of the air gap and jump to the ground electrode. Making the end of the electrode as near a sharp point as possible focuses the force of the voltage on a smaller area and makes it easier for the spark to jump.

But combustion activity erodes any sharp metal edge that is exposed to it, so there is a practical limit to how fine a rod can be used as a plug electrode. What this limit is depends on the material used, and metals like platinum, palladium, and iridium are very much more resistant to such erosion than steel.

So, then, the reason for iridium is to make the electrode finer so the spark will jump easier, what will that do for you? Better starting, mostly. Most dirt bikes generate their own electricity, and not much of it at cranking speeds. The ignition may be operating at minimum energy levels when starting, and there isn't always enough juice at the plug to fire it every single time, especially if the plug is semi fouled. Lower spark voltage may short through the deposits on the plug instead of jumping the gap. An iridium plug helps this. Also, at extremely high RPM, some systems don't have time to build a full strength spark between firings, and here again, the finer electrodes can help.

But, if you never experience any of these problems, and your normal plug holds up OK, using iridium, etc., plugs will do nothing for you.

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No, iridium plugs are what four strokes run. I have a crf450r and I run an iridium plug in mine. There is no reason for a two stroke to run one because it would run very hot as iridium is a hot metal. I would stick with the br8eg cause thats as hot as you should go trails or track thats all i used to run in my two strokes. I don't recommend the br9eg ethier to cold and fouls easy.

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No, iridium plugs are what four strokes run. I have a crf450r and I run an iridium plug in mine. There is no reason for a two stroke to run one because it would run very hot as iridium is a hot metal.

This is false.

The heat range of the spark plug is not controlled by anything relative to the electrode, and an NGK iridium plug with a heat range of 8 is the same as a standard NGK plug with a heat range of 8.

Heat range is determined by the amount of exposed porcelain on the plug insulator, and is only about keeping the spark plug within a certain temperature range, not controlling combustion chamber temperatures. The larger combustion exposed insulator is, the more slowly it can conduct heat away from the electrode, and as it cools more slowly, the plug will stay hotter than if it had a shorter insulator.

A "colder" plug will not make the engine run cooler, unless you count the fact that engines that have shut down because of a fouled plug do run cooler than when they are running. Plugs with too high a heat range can cause problems that indirectly increase engine heat if they lead to the plug becoming hot enough top pre-ignite the fuel charge, which then it turn leads to detonation, or timing related heat problems.

Interestingly, it is possible for a plug to end up causing pre-ignition because it's too cold. If a plug is cold enough that deposits form without burning away, but not so cold that it fouls and shorts out quickly, the deposits can form a "hot spot" that glows red under compression heat.

The purpose of selecting the plug's heat range is to find the lowest heat range at which the plug will burn itself clean reasonably well so that it doesn't end up shorting through the build up of deposits, and that's it. The material used in the electrode has nothing whatever to do with it.

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As grey racer said above, the iridium plug wont give you more power per se, but its finer point will allow the spark to jump the gap more easily under difficult conditions, ie Higher compression ect. So you only see an increase of power if the standard plug is struggling because of any mods, i doubt a standard engine would need it.

Having said that I use one, because my plug is an absolute swine to change and because the iridium tends to last longer than a standard plug i dont have to change it as often. My alfa 156 v6 used platinum plugs for that very reason (manifold off etc)

I also believe the imprezza uses them for the rear plugs only because they're difficult to change... Fronts are normal plugs.

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I'm sorry but that is not true, your two stroke motor with a br8eg will run at least 10 degrees warmer, with a br9eg i will run 10 degrees cooler etc. Hotter plugs create more spark and colder plugs make less. So there fore the motor will run warmer. Not trying to be a dick but I thought id point that out cause if they make hotter and colder plugs but they didn't really get any hotter or colder why would they make them?

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I've always taken it as the heat value of the plug dictates how hot the plug electrode gets, not the engine. I cant see how the spark plug would affect the temp of the engine itself, given its comparatively tiny surface area compared to the combustion chamber. i might be wrong, what are your reasons for saying that?

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I'm sorry but that is not true, your two stroke motor with a br8eg will run at least 10 degrees warmer, with a br9eg i will run 10 degrees cooler etc. Hotter plugs create more spark and colder plugs make less. So there fore the motor will run warmer. Not trying to be a dick but I thought id point that out cause if they make hotter and colder plugs but they didn't really get any hotter or colder why would they make them?

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I'm sorry but that is not true, your two stroke motor with a br8eg will run at least 10 degrees warmer, with a br9eg i will run 10 degrees cooler etc. Hotter plugs create more spark and colder plugs make less. So there fore the motor will run warmer. Not trying to be a dick but I thought id point that out cause if they make hotter and colder plugs but they didn't really get any hotter or colder why would they make them?

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You think he'll actually read that? Or just come back and tell people they are wrong?

What I like about this forum, if Grey chimes in, he's probably got a pretty good idea what he's talking about, and unless you work in the field that is being discussed, or do a lot of research in it, it's best just to take notes and listen. And that also goes for several other guys in here. It's nice to get straight answers. Now I could imagine the plug temp effecting the jetting, and rich or lean jetting would effect the temp, but that's cause by poor jetting and not the plug. I also say iridium is too expensive when you change plugs as often as you do in dirtbikes.

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In my experinece , we have had more of the ends drop off an iridium plug than any other type , i.e. an EG plug- We have run them on YZ125 , YZ144 , they were especially prone to dropping their ends off on the 144... but detonation was a regular problem on that bike.

It does make a mess on the top of the piston and also the head , we have always run the recommended heat range , BR9EIX,BR9EG..

Because of this , we tend to steer clear of the iridiums' now , and buy 2 EG for the same price.

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I've run fine wire and "irridium" plugs for the reasons Grey posted, the most notable effect is easier starting. From my 2T days I always carried a spare plug, now I just change once a year "just in case". First thing to change if I'm having engine operating problems is the plug because it is easy and it eliminate one possible.